Design Considerations and Strengthening Mechanisms in Developing Co-Re-Based Alloys for Applications at + 100°C above Ni-Superalloys

Volume 3: Cycle Innovations; Education; Electric Power; Fans and Blowers; Industrial and Cogeneration

et al. 2012

Conceptual turbine and compressor designs have been established for the semi-closed oxy-fuel combustion combined cycle and the Graz cycle. Real gas effects are addressed by extending cycle and conceptual design tools with a fluid thermo-dynamic and transport property database. Maximum compressor efficiencies are established by determining optimal values for stage loading, degree of reaction and number of compressor stages. Turbine designs are established based on estimates on achievable blade root stress levels and state of the art design parameters. The work indicates that a twin shaft geared compressor is needed to keep stage numbers to a feasible level. The Graz cycle is expected to be able to deliver around 3% net efficiency benefit over the semi-closed oxy-fuel combustion combined cycle at the expense of a more complex realization of the cycle.

Section: Conceptual Turbine Designmentioning

confidence: 99%

A Comparative Analysis of Two Competing Mid-Size Oxy-Fuel Combustion Cycles

Thorbergsson

Grönstedt

Volume 3: Cycle Innovations; Education; Electric Power; Fans and Blowers; Industrial and Cogeneration

et al. 2012

“…Figure 2 shows the Sovran and Klomp chart for the performance of a conical diffuser In SCOC-CC, the combustion outlet temperature was higher due to changing gas turbine working fluid and was set to 1400 C. This firing level exceeds the blade material limitations. The study assumed using high temperature material such as fourth generation single crystal alloys in manufacturing turbine blades [26,27]. Thus the stator metal temperature was set to 950 C, while the rotor metal temperature was set to 920 C. The metal temperature is a function of the material properties and cooling technique.…”

Section: Dimensionless Mass Flowmentioning

confidence: 99%

Conceptual Mean-Line Design of Single and Twin-Shaft Oxy-Fuel Gas Turbine in a Semi-Closed Oxy-Fuel Combustion Combined Cycle

Volume 3: Cycle Innovations; Education; Electric Power; Fans and Blowers; Industrial and Cogeneration

Genrup

Thorbergsson

et al. 2012

The aim of this study was to compare single- and twin-shaft oxy-fuel gas turbines in a semi-closed oxy-fuel combustion combined cycle (SCOC-CC). This paper discussed the turbomachinery preliminary mean-line design of oxy-fuel compressor and turbine. The conceptual turbine design was performed using the axial through-flow code LUAX-T, developed at Lund University. A tool for conceptual design of axial compressors developed at Chalmers University was used for the design of the compressor. The modeled SCOC-CC gave a net electrical efficiency of 46% and a net power of 106 MW. The production of 95% pure oxygen and the compression of CO2 reduced the gross efficiency of the SCOC-CC by 10 and 2 percentage points, respectively. The designed oxy-fuel gas turbine had a power of 86 MW. The rotational speed of the single-shaft gas turbine was set to 5200 rpm. The designed turbine had four stages, while the compressor had 18 stages. The turbine exit Mach number was calculated to be 0.6 and the calculated value of AN2 was 40·106 rpm2m2. The total calculated cooling mass flow was 25% of the compressor mass flow, or 47 kg/s. The relative tip Mach number of the compressor at the first rotor stage was 1.15. The rotational speed of the twin-shaft gas generator was set to 7200 rpm, while that of the power turbine was set to 4500 rpm. Twin-shaft turbine designed with five turbine stages to maintain the exit Mach number around 0.5. The twin-shaft turbine required a lower exit Mach number to maintain reasonable diffuser performance. The compressor turbine was designed with two stages while the power turbine had three stages. The study showed that a four-stage twin-shaft turbine produced a high exit Mach number. The calculated value of AN2 was 38·106 rpm2m2. The total calculated cooling mass flow was 23% of the compressor mass flow, or 44 kg/s. The compressor was designed with 14 stages. The preliminary design parameters of the turbine and compressor were within established industrial ranges. From the results of this study it was concluded that both single- and twin-shaft oxy-fuel gas turbines have advantages. The choice of a twin-shaft gas turbine can be motivated by the smaller compressor size and the advantage of greater flexibility in operation, mainly in off-design mode. However, the advantages of a twin-shaft design must be weighed against the inherent simplicity and low cost of the simple single-shaft design.

“…In SCOC-CC, the combustion outlet temperature was higher due to changing gas turbine working fluid and was set to 1400 C. This firing level exceeds the blade material limitations. The study assumed using high temperature material such as fourth generation single crystal alloys in manufacturing turbine blades [26,27]. Thus the stator metal temperature was set to 950 C, while the rotor metal temperature was set to 920 C. The metal temperature is a function of the material properties and cooling technique.…”

Section: Dimensionless Mass Flowmentioning

confidence: 99%

Conceptual Mean-Line Design of Single and Twin-Shaft Oxy-Fuel Gas Turbine in a Semiclosed Oxy-Fuel Combustion Combined Cycle

Journal of Engineering for Gas Turbines and Power

Thorbergsson²,

Grönstedt

et al. 2013

The aim of this study was to compare single-and twin-shaft oxy-fuel gas turbines in a semiclosed oxy-fuel combustion combined cycle (SCOC-CC). This paper discussed the turbomachinery preliminary mean-line design of oxy-fuel compressor and turbine. The conceptual turbine design was performed using the axial through-flow code LUAX-T, developed at Lund University. A tool for conceptual design of axial compressors developed at Chalmers University was used for the design of the compressor. The modeled SCOC-CC gave a net electrical efficiency of 46% and a net power of 106 MW. The production of 95% pure oxygen and the compression of CO 2 reduced the gross efficiency of the SCOC-CC by 10 and 2 percentage points, respectively. The designed oxy-fuel gas turbine had a power of 86 MW. The rotational speed of the single-shaft gas turbine was set to 5200 rpm. The designed turbine had four stages, while the compressor had 18 stages. The turbine exit Mach number was calculated to be 0.6 and the calculated value of AN 2 was 40 Á 10 6 rpm 2 m 2 . The total calculated cooling mass flow was 25% of the compressor mass flow, or 47 kg/s. The relative tip Mach number of the compressor at the first rotor stage was 1.15. The rotational speed of the twin-shaft gas generator was set to 7200 rpm, while that of the power turbine was set to 4800 rpm. A twin-shaft turbine was designed with five turbine stages to maintain the exit Mach number around 0.5. The twin-shaft turbine required a lower exit Mach number to maintain reasonable diffuser performance. The compressor turbine was designed with two stages while the power turbine had three stages. The study showed that a four-stage twin-shaft turbine produced a high exit Mach number. The calculated value of AN 2 was 38 Á 10 6 rpm 2 m 2 . The total calculated cooling mass flow was 23% of the compressor mass flow, or 44 kg/s. The compressor was designed with 14 stages. The preliminary design parameters of the turbine and compressor were within established industrial ranges. From the results of this study, it was concluded that both single-and twin-shaft oxy-fuel gas turbines have advantages. The choice of a twin-shaft gas turbine can be motivated by the smaller compressor size and the advantage of greater flexibility in operation, mainly in the off-design mode. However, the advantages of a twin-shaft design must be weighed against the inherent simplicity and low cost of the simple single-shaft design.